The present invention relates to hydraulic vibration-damping supports serving, for example, for mounting motor vehicle engines on the bodies of such vehicles.
More precisely, in a first aspect, the invention relates to a hydraulic vibration-damping support serving to interconnect first and second rigid elements so as to damp and filter vibration between said elements, the support comprising:
first and second rigid strength members serving to be fixed to respective ones of the first and second rigid elements to be interconnected;
an elastomer body interconnecting the first and second strength members;
a first chamber filled with liquid, and defined at least in part by the elastomer body; and
a decoupling device comprising firstly first and second parallel gratings that are generally plane in shape, and secondly a decoupling valve member which is in the form of an elastomer pad and which has first and second faces provided with projecting studs made of elastomer, the decoupling valve member being mounted with clearance between the first and second gratings with the first and second faces of said decoupling valve member disposed facing respective ones of the first and second gratings, and said decoupling valve member being suitable for closing off said gratings, said first grating communicating with the first chamber and the second grating communicating with a second chamber suitable for enabling the decoupling valve member to vibrate freely between the two gratings when the first and second strength members are subjected to relative vibratory movements (in practice, the second chamber is usually constituted by a compensation chamber filled with liquid and connected to the first chamber via a constricted passage, but it may optionally be some other deformable hydraulic chamber or indeed a pneumatic chamber).
Document FR-A-2 674 590 describes an example of such a vibration-damping support which operates quite satisfactorily, in particular to avoid or to limit banging of the valve member against the gratings, which generates vibration and/or noise that is unpleasant for the users of the vehicle.
However, it has become apparent that it would be useful to improve vibration-damping supports of this type, in particular to achieve further improvement in their performance.
To this end, in the first aspect of the invention, in a vibration-damping support of the type in question the studs of the decoupling valve member are disposed so that, in the absence of relative vibration between the first and second strength members, the decoupling valve member is held in a rest position in which said valve member has a midplane disposed on a slant relative to the first and second gratings.
In preferred embodiments of the vibration-damping support in the first aspect of the invention, it is optionally possible, in addition, to use any of the following provisions:
the studs of the decoupling valve member comprise outer studs which are disposed in the vicinity of an outer periphery of said decoupling valve member and which are distributed in first and second groups of outer studs disposed on either side of a geometrical construction line extending across the decoupling valve member parallel to the midplane of said decoupling valve member, the first group of outer studs being situated on the first face, and the second group of outer studs being situated on the second face of said decoupling valve member;
the decoupling valve member is in the shape of a circular disk having a center through which a diametrical line constituting said construction line passes;
the outer studs of the first group are symmetrical to the outer studs of the second group about said construction line;
the decoupling valve member is provided with first and second elastomer centering lugs disposed at the center of the decoupling valve member on respective ones of the two faces of said decoupling valve member, said first and second centering lugs co-operating with respective ones of the two gratings to center the decoupling valve member relative to said gratings, the studs of the decoupling valve member further comprising inner studs disposed in the vicinity of the center of said decoupling valve member on both faces of said decoupling valve member;
the decoupling valve member is provided with two inner studs disposed in the vicinity of the first centering lug, symmetrically about said construction line;
the second centering lug is clipped into one of the gratings, and the decoupling valve member is provided with two inner studs disposed close to the second centering lug, on the side of said construction line opposite to its side on which the outer studs of the second group are situated;
the decoupling valve member is further provided with rounded elastomer projections which are distributed over the entire first and second faces of said decoupling valve member, and which project towards respective ones of the first and second gratings, the studs extending beyond said round projections from the first and second faces of the decoupling valve member;
the decoupling valve member is further provided with an outer peripheral rim projecting towards the first and second gratings from the first and second faces of the decoupling valve member, said peripheral rim being flush with the rounded projections of said first and second faces;
the second chamber is filled with liquid and is defined at least in part by a flexible elastomer wall, a constricted passage putting the first and second chambers into communication with each other;
the elastomer body is bell-shaped so that it diverges about a central axis between a top secured to the first strength member and an annular base secured to the second strength member, and the vibration-damping support further comprises a deflector in the form of an annular ring that extends inside the first chamber by surrounding the first grating and by converging towards the top of the elastomer body, said constricted passage opening out in the first chamber outside the deflector;
the first and second gratings are part of a rigid partition which separates the first and second chambers, the deflector including an abutment margin which extends parallel to said rigid partition and which is clamped between the base of the elastomer body and said rigid partition;
the deflector converges towards a flat top extending substantially parallel to the first and second gratings, the flat top having an annular rim which extends over a certain width and which surrounds an opening itself having a certain diameter, the width of the rim lying in the range 2% of the diameter of the opening to 5% of the diameter of the opening.
In addition, in a second aspect, the invention relates to a hydraulic vibration-damping support serving to interconnect first and second rigid elements so as to damp and filter vibration between said elements, the support comprising:
first and second rigid strength members serving to be fixed to respective ones of the first and second rigid elements to be interconnected;
an elastomer body that is substantially bell-shaped, extending about a central axis between a top secured to the first strength member and an annular base secured to the second strength member;
a working chamber filled with liquid and defined at least in part by the elastomer body;
a compensation chamber filled with liquid and defined at least in part by a flexible elastomer wall;
a rigid partition that separates the working chamber from the compensation chamber, which rigid partition comprises a sheet metal first piece that is in leaktight contact with the annular base of the elastomer body, and a rigid second piece that is in leaktight contact with said sheet metal first piece and that co-operates with the flexible wall to define the compensation chamber, the sheet metal first piece being provided with a first central grating that communicates with the working chamber, and the rigid second piece being provided with a second central grating that communicates with the compensation chamber while co-operating with the first grating to define a valve member recess;
a decoupling valve member disposed in the valve member recess to move over a short stroke parallel to the central axis to close off the first and second gratings; and
a constricted passage filled with liquid and that puts the working chamber into communication with the compensation chamber, the constricted passage being defined in part by the sheet metal first piece and by the rigid second piece of the rigid partition, said constricted passage extending angularly around the decoupling valve member over a linear length that is greater than the perimeter of the rigid partition, and said constricted passage being made up of first and second stages, the first stage of the constricted passage being adjacent to the working chamber and extending between a first end that communicates with the working chamber and a second end that communicates with the second stage, while the second stage of the constricted passage is adjacent to the compensation chamber and extends between a first end which communicates with the second end of the first stage and a second end which communicates with the compensation chamber.
A hydraulic vibration-damping support of that type is disclosed, for example, in Document FR-A-2 751 042, in which the rigid second piece of the rigid partition is a casting.
That known vibration-damping support is quite satisfactory as regards technical operation. In particular, it is known that the resonance frequency of the constricted passage, which resonance frequency is also the frequency at which the vibration-damping support offers its best performance for large-amplitude vibration, depends on the ratio between the length and the equivalent diameter of the constricted passage: by implementing the constricted passage in two stages, it is thus possible to obtain a passage length that is long and thus a resonance frequency that is low for said constricted passage, which can be necessary in certain uses.
Unfortunately, the above-mentioned vibration-damping support suffers from the drawback that the casting of its rigid partition is relatively costly to make, and also relatively weighty, which tends to increase both the cost and the weight of the vibration-damping support.
A particular object of the present invention is to mitigate those drawbacks.
To this end, in a vibration-damping support of the type in question:
the rigid second piece of the rigid shell is constituted by a second piece of sheet metal that is cut out and stamped;
the flexible elastomer wall is secured to a rigid base which is itself secured to the second strength member and which has at least one side wall extending about the central axis from the second strength member to an inner annular abutment margin;
the second piece of sheet metal includes an outer annular abutment margin that is in leaktight contact with the inner annular abutment margin of the base, the second piece of sheet metal further including a step which extends about the central axis from said outer annular abutment margin to a non-perforated annular zone that is in leaktight contact with the first piece of sheet metal, the second stage of the constricted passage being defined between the first piece of sheet metal, the side wall of the base, the inner annular abutment margin of the base, the outer annular abutment margin of the second piece of sheet metal, and the step of said second piece of sheet metal;
and the first stage of the constricted passage is defined between the annular base of the elastomer body, and the first piece of sheet metal.
By means of these provisions, it is possible to obtain a constricted passage that is very long, extending over two stages, by using a partition that is merely made up of two pieces of sheet metal, and that is therefore particularly lightweight and inexpensive.
In preferred embodiments of the vibration-damping support the invention, it is optionally possible, in addition, to use any of the following provisions:
the second strength member includes an annular inner portion which is part of the base of the elastomer body and which forms a groove that is open facing towards the first piece of sheet metal, said groove co-operating with said first piece of sheet metal to define the first stage of the constricted passage, the first and second ends of the first stage of the constricted passage being separated from each other by an elastomer stopper that is part of the elastomer body;
the first piece of sheet metal is provided with an outer annular rim that extends about the central axis towards the second strength member to a free annular edge that is applied axially in leaktight contact against an outer portion of the second strength member, the inner portion of the second strength member being provided with an inner skirt that is extended parallel to the central axis beyond said free annular edge to come into contact with a radial annular portion that is part of the first piece of sheet metal, the first stage of the constricted passage being defined in part by said inner skirt and by said outer rim of the first piece of sheet metal;
the first piece of sheet metal includes a non-perforated annular portion which is in leaktight axial contact with the second piece of sheet metal and which is extended inwards by an annular step that is itself extended by the first grating, the valve member recess being defined laterally by said annular step of the first piece of sheet metal;
the first stage of the constricted passage communicates with the second stage of the constricted passage via an opening cut out in the first piece of sheet metal, and the second stage of the constricted passage communicates with the compensation chamber via an opening cut out in the second piece of sheet metal;
the opening cut out in the second piece of sheet metal is provided at least in the outer annular abutment edge and in the step of said second piece of sheet metal, the first and second ends of the second stage of the constricted passage being separated from each other by an elastomer stopper molded integrally with the flexible elastomer wall against an inner face of the inner abutment margin and an inner face of the side wall of the base, said elastomer stopper of the base penetrating in part into the opening in the second piece of sheet metal, and the second grating having a non-perforated portion that is applied axially in leaktight contact against said elastomer stopper of the base;
the elastomer stopper of the base is provided with a slot that is open axially towards the elastomer body and laterally towards the first end of the second stage of the constricted passage, the step of the second piece of sheet metal having an edge that laterally defines the opening cut out in said second piece of sheet metal and that penetrates into said slot;
the flexible elastomer wall is molded over the base so that it forms extra thickness in the vicinity of the elastomer stopper of the base, the opening cut out in the second piece of sheet metal forming two edges in the outer annular abutment margin of said second piece of sheet metal, the two edges being disposed on either side of the elastomer stopper of the base and on either side of said extra thickness; and
the elastomer stopper of the base is provided with a stud that projects axially towards the elastomer body, and the first piece of sheet metal includes a portion that comes into leaktight axial abutment against the elastomer stopper of the base, and that is provided with a hole in which the stud is engaged.